1. Field
This invention relates to an information processing apparatus capable of outputting an encrypted digital video signal and a video signal output control method.
2. Description of the Related Art
Presently, digital broadcasting is becoming mainstream in place of analog broadcasting. Digital-signal-recorded sources, such as DVDs, have been used. With the transition from analog to digital broadcasting, it is conceivable that digital signals will be output directly to a TV set.
In the case of digital output, since use of high-quality video content is possible, it is necessary to strengthen copyright protection to prevent provided video content from being reproduced in an unauthorized manner or copied illegally. As digital content protection techniques, the HDCP (High-bandwidth Digital Content Protection System) standard has been proposed.
The HDCP standard is a standard for transferring the video content requiring copyright protection safely in a digital video signal transmission system. The HDCP standard prescribes specifications for authentication between the transmitting unit and the receiving unit, the sharing of a key for authentication, the encryption of video signals to be transmitted, and others.
In authentication in the HDCP standard or the like, a device key for authenticating the other party's device individually by public key encryption is used. If authentication is successful between the transmitting unit and the receiving unit, the transmitting unit encrypts the video signal using the device key and transmits the encrypted signal. The receiving unit decrypts the received video signal using the device key. For example, a digital image transmitting apparatus using an authentication method complying with the HDCP standard or the like has been disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-314970.
When a notebook personal computer is used as an information output apparatus, use of a docking station can be considered in order to output a signal to a TV set. In a state where the personal computer is installed on the docking station and the encrypted video signal is output to the TV set, suppose the personal computer (or an information processing apparatus) is removed from the docking station (or an external unit). In this case, there is a possibility that the personal computer will kept outputting the video signal.